Composite bicycle frames, such as those made of carbon fiber, are well known.
The advantage provided by composite bicycle frames is that they tend to be lighter than bicycle frames made from other materials, such as metals, while still providing the necessary structure required to support the loads generated while using the bicycle.
Certain composite bicycle frames are sometimes (incorrectly) referred to as being “monocoque”. Such known carbon fiber tubular frames are typically composed of a number of separate tubular composite and/or metal components which are joined together to form the final composite “uni-body” frame. Most composite tubular frames are therefore not integrally formed, one-piece designs, much less “monocoque” in the sense of the term typically understood by most engineers, as will be defined in further detail below.
In fact, known composite tubular bicycle frames sometimes more closely resemble conventional, or “lug type”, bicycle frames, which are made of individual components joined together with welds, mechanical fasteners and/or adhesives. Examples of certain known bicycle frames, as well as methods for manufacturing them, are provided in U.S. Pat. No. 5,368,804 and in U.S. Pat. No. 5,803,476.
While attempts have been made to mold composite bicycle frames, rather than forming them by more traditional carbon fiber lay-up and curing processes, the molds used can be difficult to manipulate, expensive to operate, and costly to manufacture. Yet another known disadvantage relates to the molding process itself, which is time consuming because of the manual labor involved, especially for highly complex tubular shapes and connections. Often, the composite material must be “laid-up” within the mold by hand, which can further increase labour costs, production cycles and therefore end-product cost. Furthermore, it is difficult to control some of the properties of known molded composite frames, such as their thickness, when using conventional molding processes. This consequently inhibits the rapid production of composite frames of uniform weight.